In a telescopic boom telescopic system with more than six boom sections, since a rope aligning mechanism is relatively complex to use, a telescopic device of single-cylinder latch type is commonly used at present. The so-called telescopic device of single-cylinder latch type is a mechanism which adopts a single telescopic cylinder to achieve extension and retraction of a telescopic boom, and the extension and retraction of the telescopic boom are achieved by the cooperation of cylinder pin and boom pins.
The existing telescopic device of single-cylinder latch type mainly adopts an upper boom pin solution. Namely, a boom pin is mounted at the upper part of each boom section except a basic boom section, and a T-shaped groove is driven by two boom pin cylinders to move up and down to plug in and pull out the boom pin, the two boom pin cylinders are symmetrically distributed on the head of the T-shaped groove. Due to space limitation, there is a certain distance between a point of action of the cylinder and the force bearing point of the T-shaped groove, i.e., there is a certain unbalance loading torque, resulting in that the boom pin cylinders bear an unbalance loading force. If working under the unbalance loading force for a long time, the boom pin cylinders will be subject to an oil leakage phenomenon resulting from seal wear and crush.
According to the existing telescopic device of single-cylinder latch type, in the case of larger flexural deformation of a telescopic boom, an boom pin hole of the telescopic boom is deformed due to the flexibility of the telescopic boom, so that when the boom pin is plugged in and pulled out, the boom pin is subject to a misalignment problem with the boom pin hole of the telescopic boom, which will cause the problem that the boom pin is difficult to plug in and pull out, the boom pin fails to be plugged in or pulled out resulting from an inaccurate release position of the boom pin or the like.